I ended up hack sawing mine off and then driving the remaining stubs several inches into the crossbar with a socket extension and hammer. Then I just bought new ones and started over. Of course you have to remove the set screws first. I used an impact driver. I also used anti-seize on the new adjusters and the locking screws. I replaced the screws with hex head bolts. The slotted screw heads just strip out too easy. If your boat has been around salt water most of its life this is about the only solution.